CN108182951B - Magnetic recording medium, method for manufacturing magnetic recording medium, and magnetic recording/reproducing apparatus - Google Patents

Magnetic recording medium, method for manufacturing magnetic recording medium, and magnetic recording/reproducing apparatus Download PDF

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CN108182951B
CN108182951B CN201711284415.6A CN201711284415A CN108182951B CN 108182951 B CN108182951 B CN 108182951B CN 201711284415 A CN201711284415 A CN 201711284415A CN 108182951 B CN108182951 B CN 108182951B
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magnetic
layer
magnetic layer
recording medium
magnetic recording
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CN108182951A (en
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长谷川浩太
大桥荣久
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Lishennoco Co ltd
Resonac Holdings Corp
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Showa Denko KK
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    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62Record carriers characterised by the selection of the material
    • G11B5/64Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent
    • G11B5/66Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent the record carriers consisting of several layers
    • G11B5/672Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent the record carriers consisting of several layers having different compositions in a plurality of magnetic layers, e.g. layer compositions having differing elemental components or differing proportions of elements
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62Record carriers characterised by the selection of the material
    • G11B5/68Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/706Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
    • G11B5/70605Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material metals or alloys
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62Record carriers characterised by the selection of the material
    • G11B5/68Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/706Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
    • G11B5/70626Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62Record carriers characterised by the selection of the material
    • G11B5/72Protective coatings, e.g. anti-static or antifriction
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62Record carriers characterised by the selection of the material
    • G11B5/73Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
    • G11B5/7368Non-polymeric layer under the lowermost magnetic recording layer
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/84Processes or apparatus specially adapted for manufacturing record carriers
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/84Processes or apparatus specially adapted for manufacturing record carriers
    • G11B5/851Coating a support with a magnetic layer by sputtering

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  • Engineering & Computer Science (AREA)
  • Metallurgy (AREA)
  • Magnetic Record Carriers (AREA)
  • Manufacturing Of Magnetic Record Carriers (AREA)

Abstract

A magnetic recording medium has a soft magnetic underlayer, an alignment control layer, a perpendicular magnetic layer, and a protective layer in this order on a nonmagnetic substrate. The perpendicular magnetic layer has a1 st magnetic layer and a 2 nd magnetic layer in this order from the non-magnetic substrate side. The 2 nd magnetic layer is a magnetic layer on the outermost layer side containing magnetic particles. The 1 st magnetic layer is a magnetic layer having a granular structure in which a grain boundary portion contains an oxide. The 2 nd magnetic layer is a magnetic layer having a granular structure in which a grain boundary portion contains a nitride. The nitride is a nitride of an element contained in the magnetic particle.

Description

Magnetic recording medium, method for manufacturing magnetic recording medium, and magnetic recording/reproducing apparatus
Technical Field
The invention relates to a magnetic recording medium, a method for manufacturing the magnetic recording medium, and a magnetic recording/reproducing apparatus.
Background
In a Hard Disk Drive (HDD) which is one type of magnetic recording and reproducing apparatus, the recording density is rapidly increasing at present, and this trend is continuing in the future. Therefore, development of a magnetic recording medium and a magnetic head for recording suitable for increasing the recording density has been advanced.
Currently, a magnetic recording medium mounted on a magnetic recording and reproducing apparatus on the market is a so-called perpendicular magnetic recording medium having a perpendicular magnetic layer in which the axis of easy magnetization is mainly perpendicularly aligned (orientation) with respect to the surface of a nonmagnetic substrate. Here, the perpendicular magnetic layer is an hcp structure, and its (0002) plane is mainly aligned in parallel with the surface of the non-magnetic substrate. In the case of a perpendicular magnetic recording medium having a high recording density, the influence of the back-magnetic field in the boundary region between the recording cells (bits) is small, and a sharp recording cell boundary can be formed, so that an increase in noise can be suppressed. In addition, since the perpendicular magnetic recording medium has a small reduction in the volume of the recording unit when the recording density is increased, the effect of thermal fluctuation resistance is excellent. For this reason, various structures of perpendicular magnetic recording media have been proposed.
A magnetic layer of granular (granular) structure is used in the magnetic recording layer of the perpendicular magnetic recording medium.
The magnetic layer having a granular structure is a magnetic layer having a structure in which the periphery of magnetic crystal grains is surrounded by grain boundaries of a nonmagnetic non-metallic substance such as an oxide or a nitride. Accordingly, the magnetic particles can be physically separated by the grain boundary portion of the non-magnetic non-metallic substance, so that the magnetic interaction between the magnetic particles is small, the formation of the zigzag magnetic wall at the transition region of the recording unit can be suppressed, and the noise characteristics can be improved.
On the other hand, it is also known that, in the magnetic layer having a granular structure, C o atoms and the like contained in the magnetic layer are relatively easily precipitated, and therefore, the corrosion resistance of the magnetic recording medium is remarkably deteriorated.
For this reason, it is also known to use a magnetic layer having a non-granular structure on the outermost layer side of the magnetic layer constituting the magnetic recording medium (see, for example, patent document 1).
On the other hand, example 3 of patent document 2 also describes a magnetic recording medium using BN in the grain boundary portion of the magnetic layer having a granular structure.
[ Prior art documents ]
[ patent document ]
[ patent document 1] (Japanese patent application laid-open No. 2006-277950)
Japanese patent document 2 (Japanese) laid-open No. 2001-291230
Disclosure of Invention
[ problems to be solved by the invention ]
As described above, in a magnetic recording medium, a magnetic layer of a granular structure is often used in order to improve noise characteristics; however, since it is necessary to improve corrosion resistance, a magnetic layer having a non-granular structure is used as the outermost magnetic layer. Therefore, not only improvement of the noise characteristics of the magnetic recording medium is hindered, but also high recording density of the magnetic recording medium is hindered because the magnetic grains on the outermost layer side of the magnetic layer are larger than those on the lower layer side.
The present invention has been made to solve the above problems, and an object of the present invention is to provide a magnetic recording medium having excellent noise characteristics and suitable for increasing the recording density.
[ means for solving problems ]
(1) A magnetic recording medium has a soft magnetic underlayer, an alignment control layer, a perpendicular magnetic layer, and a protective layer in this order on a nonmagnetic substrate. The perpendicular magnetic layer has a1 st magnetic layer and a 2 nd magnetic layer in this order from the non-magnetic substrate side. The 2 nd magnetic layer is a magnetic layer on the outermost layer side containing magnetic particles. The 1 st magnetic layer is a magnetic layer having a granular structure in which a grain boundary portion contains an oxide. The 2 nd magnetic layer is a magnetic layer having a granular structure in which a grain boundary portion contains a nitride. The nitride is a nitride of an element contained in the magnetic particle.
(2) In the magnetic recording medium described in the preceding item (1), the element contained in the magnetic particles is boron, titanium, chromium, aluminum, tantalum, zirconium, or silicon.
(3) In the magnetic recording medium described in the preceding item (1) or (2), the oxide is an oxide of silicon, chromium, titanium, tantalum, aluminum, yttrium, boron, magnesium, tungsten, or cobalt.
(4) A method for manufacturing a magnetic recording medium having a soft magnetic underlayer, an alignment control layer, a perpendicular magnetic layer, and a protective layer in this order on a nonmagnetic substrate. The step of forming the perpendicular magnetic layer includes a step of forming a1 st magnetic layer and a step of forming a 2 nd magnetic layer in this order. The 2 nd magnetic layer is formed as a magnetic layer on the outermost layer side containing magnetic particles. The step of forming the 1 st magnetic layer is a step of forming a magnetic layer having a granular structure in which an oxide is included in a grain boundary portion by a sputtering method. The step of forming the 2 nd magnetic layer is a step of forming a magnetic layer having a granular structure by forming a magnetic layer having a non-granular structure by a sputtering method and then nitriding the magnetic layer to form a grain boundary portion by nitriding a part of elements contained in the magnetic particles.
(5) The method of manufacturing a magnetic recording medium described in the preceding item (4), wherein the nitrided element is boron, titanium, chromium, aluminum, tantalum, zirconium or silicon.
(6) In the production method of a magnetic recording medium described in the preceding item (4) or (5), the oxide is an oxide of silicon, chromium, titanium, tantalum, aluminum, yttrium, boron, magnesium, tungsten, or cobalt.
(7) A magnetic recording/reproducing apparatus having the magnetic recording medium of any one of the preceding items (1) to (3) and a magnetic head which performs recording and reproduction of information on the magnetic recording medium.
[ Effect of the invention ]
According to the present invention, it is possible to provide a magnetic recording medium having excellent noise characteristics and suitable for increasing the recording density.
Drawings
FIG. 1 is a vertical cross-sectional view showing a structure of an example of a magnetic recording medium according to an embodiment.
FIG. 2 is a longitudinal sectional view showing the structure of the perpendicular magnetic layer of FIG. 1.
FIG. 3 is a schematic view showing an example of a magnetic recording/reproducing apparatus according to the embodiment.
[ description of symbols ]
1 non-magnetic substrate
2 Soft magnetic underlayer
3 alignment controlling layer
4 perpendicular magnetic layer
5 protective layer
6 lubricating layer
4a 1 st magnetic layer
4b 2 nd magnetic layer
7 a-7 e magnetic or non-magnetic layer
8 nonmagnetic underlayer
10 magnetic recording medium
11 medium drive unit
12 magnetic head
13 magnetic head driving part
14 recording/reproducing signal processing system
41 magnetic or non-magnetic particles
42 grain boundary part
Detailed Description
The magnetic recording medium, the method for manufacturing the same, and the magnetic recording and reproducing device according to the embodiments of the present invention will be described in detail below.
Fig. 1 shows a structure of an example of a magnetic recording medium according to the present embodiment.
The magnetic recording medium 10 has a soft magnetic underlayer 2, an orientation control layer 3, a perpendicular magnetic layer 4, a protective layer 5, and a lubricating layer 6 in this order on a nonmagnetic substrate 1.
The perpendicular magnetic layer 4 includes a1 st magnetic layer 4a and a 2 nd magnetic layer 4b in this order from the nonmagnetic substrate 1 side, and further includes arbitrary magnetic layers or nonmagnetic layers 7a, 7b, 7c, 7d, and 7 e. In the perpendicular magnetic layer 4, as shown in fig. 2, the magnetic particles or non-magnetic particles 41 form continuous columnar crystals from the lower layer to the upper layer. In addition, the grain boundary portion 42 of the 1 st magnetic layer 4a contains an oxide, and the grain boundary portion 42 of the 2 nd magnetic layer 4b contains a nitride.
Here, in the 1 st magnetic layer 4a and the 2 nd magnetic layer 4b, 41 is a magnetic particle, and in the case where 7a, 7b, 7c, 7d, and 7e are magnetic layers (or non-magnetic layers), 41 is a magnetic particle (or a non-magnetic particle).
As the nonmagnetic substrate 1, a metal substrate made of a metal material such as aluminum or an aluminum alloy may be used, and a nonmetal substrate made of a nonmetal material such as glass, ceramic, silicon carbide (silicon carbide), or carbon may be used.
As the nonmagnetic substrate 1, a substrate in which a NiP layer or a NiP alloy layer is formed on the surface of the above-described metal substrate or nonmetal substrate by a plating method or a sputtering method can be used.
The soft magnetic underlayer 2 is provided for the purpose of increasing the component of the magnetic flux generated by the magnetic head with respect to the perpendicular direction of the nonmagnetic substrate 1 and more firmly fixing the direction perpendicular to the magnetization easy axis of the magnetic layer 4 in the direction perpendicular to the nonmagnetic substrate 1. This effect is particularly remarkable when a single-pole magnetic head for perpendicular recording is used as the recording head.
The material constituting the soft magnetic underlayer 2 is not particularly limited, and a soft magnetic material containing Fe, Ni, and Co can be used.
Examples of the soft magnetic material include CoFe-based alloys (CoFeTaZr, CoFeZrNb, etc.), FeCo-based alloys (FeCo, FeCoV, etc.), FeNi-based alloys (FeNi, FeNiMo, FeNiCr, FeNiSi, etc.), FeAl-based alloys (FeAl, fealsisi, FeAlSiCr, fealtiru, FeAlO, etc.), FeCr-based alloys (FeCr, FeCrTi, FeCrCu, etc.), FeTa-based alloys (FeTa, FeTaC, FeTaN, etc.), femmg-based alloys (femmgo, etc.), FeZr-based alloys (FeZrN, etc.), FeC-based alloys, FeN-based alloys, FeSi-based alloys, FeP-based alloys, fennb-based alloys, FeHf-based alloys, FeB-based alloys, and the like.
The soft magnetic underlayer 2 is preferably composed of 2 layers of soft magnetic layers, and a Ru film is provided between the 2 layers of soft magnetic layers.
In this case, the thickness of the Ru film is preferably adjusted to a range of 0.4 to 1.0nm or 1.6 to 2.6 nm. Accordingly, the 2-layer soft magnetic layer can be an AFC structure, and so-called spike noise (spike noise) can be suppressed.
An adhesion layer is preferably provided between the nonmagnetic substrate 1 and the soft magnetic underlayer 2. By bringing the nonmagnetic substrate 1 into contact with the soft magnetic underlayer 2 containing Co or Fe in this way, the influence of adsorbed gas or moisture on the surface of the nonmagnetic substrate 1 can be suppressed, or the progress of corrosion due to diffusion of components constituting the nonmagnetic substrate 1 can be suppressed.
Examples of the material constituting the adhesion layer include Cr, Cr alloys, Ti, and Ti alloys.
The thickness of the adhesion layer is preferably
Figure BDA0001498140930000061
The above.
The alignment control layer 3 is used to control the alignment of the perpendicular magnetic layer 4, that is, to make the hcp-structured perpendicular magnetic layer 4 mainly perform (0002) plane alignment with respect to the surface of the nonmagnetic substrate 1 and to make the magnetic crystal grains of the perpendicular magnetic layer 4 finer, thereby improving the recording and reproducing characteristics.
The material constituting the alignment control layer 3 is not particularly limited, and preferably has an hcp structure, an fcc structure, or an amorphous (amorphous) structure.
Examples of the material constituting the orientation controlling layer 3 include Ru-based alloys, Ni-based alloys, Co-based alloys, Pt-based alloys, and Cu-based alloys.
By making these alloys multilayered, the alignment control layer 3 can be formed. In this case, as the orientation controlling layer 3, for example, a multilayer structure of an Ni-based alloy and an Ru-based alloy, a multilayer structure of a Co-based alloy and an Ru-based alloy, and a multilayer structure of a Pt-based alloy and an Ru-based alloy from the side of the nonmagnetic substrate 1 are preferably used.
The perpendicular magnetic layer 4 has an hcp structure, and is mainly (0002) plane-aligned with respect to the surface of the nonmagnetic substrate 1, and the easy magnetization axis is mainly perpendicularly aligned with respect to the nonmagnetic substrate 1. The perpendicular magnetic layer 4 includes a1 st magnetic layer 4a and a 2 nd magnetic layer 4b in this order from the nonmagnetic substrate 1 side, and the 2 nd magnetic layer 4b is the magnetic layer on the outermost layer side. The 1 st magnetic layer 4a is a magnetic layer having a granular structure in which the grain boundary part 42 includes an oxide. The 2 nd magnetic layer 4b is a magnetic layer having a granular structure in which the grain boundary part 42 contains a nitride, and the nitride is a nitride of an element contained in the magnetic grains of the 2 nd magnetic layer 4 b.
The 1 st magnetic layer 4a is a magnetic layer having a granular structure in which the grain boundary portion 42 contains an oxide, but has a structure in which the periphery of the magnetic crystal grains is surrounded by an oxide. Accordingly, the grain boundary portion of the oxide can physically separate the magnetic particles, so that the magnetic interaction between the magnetic particles can be reduced, and the formation of the zigzag magnetic wall at the transition region of the recording unit can be suppressed, and thus the low noise characteristic can be obtained.
Conventionally, non-metallic non-magnetic materials such as oxides, nitrides, carbides, borides, and the like have been used in grain boundary portions of magnetic layers having a granular structure. According to the studies of the inventors of the present application, it has been found that when a magnetic layer having a granular structure is formed by a sputtering method, since the non-metallic non-magnetic material has the highest reactivity of an oxide, the film formation is easy, the magnetic particles are easily physically separated, and the magnetic interaction between the magnetic particles can be reduced.
In order to form such a structure by the sputtering method, the content of the oxide in the 1 st magnetic layer 4a and the film formation conditions of the 1 st magnetic layer 4a are important.
The content of the oxide in the 1 st magnetic layer 4a is preferably 3 mol% or more and 18 mol% or less, and more preferably 6 mol% or more and 13 mol% or less, with respect to the total mol calculated from 1 compound of a material constituting the magnetic particles, for example, an alloy of Co, Cr, Pt, or the like.
The reason why the content of the oxide in the 1 st magnetic layer 4a is preferably 3 mol% or more and 18 mol% or less is that, as shown in fig. 2, when the perpendicular magnetic layer 4 is formed, the oxide is easily precipitated at the grain boundary portion 42 around the magnetic particle 41, and the magnetic particle 41 is easily isolated and refined. If the content of the oxide in the 1 st magnetic layer 4a is 18 mol% or less, the oxide is less likely to remain in the magnetic grains 41, and as a result, the orientation and crystallinity of the magnetic grains 41 are not impaired, and the oxide is less likely to precipitate above and below the magnetic grains 41, and as a result, the magnetic grains 41 can have a columnar structure that vertically penetrates the perpendicular magnetic layer 4. In addition, if the content of the oxide in the 1 st magnetic layer 4a is 3 mol% or more, the magnetic grains 41 are easily isolated and miniaturized, and as a result, noise during recording and reproduction is reduced, and a signal-to-noise ratio (S/N ratio) suitable for high recording density can be obtained.
The oxide contained in the grain boundary portion 42 of the 1 st magnetic layer 4a is preferably an oxide of silicon, chromium, titanium, tantalum, aluminum, yttrium, boron, magnesium, tungsten, or cobalt.
As a material constituting the 1 st magnetic layer 4a, for example, CoCrPt-SiO2、CoCrPtNb-Cr2O3、CoCrPt-Ta2O5、CoCrPt-Cr2O3-TiO2、CoCrPt-Cr2O3-SiO2、CoCrPt-Cr2O3-SiO2-TiO2、CoCrPtMo-TiO2、CoCrPtW-TiO2、CoCrPtB-Al2O3、CoCrPtTaNd-MgO、CoCrPtBCu-Y2O3、CoCrPtRu-SiO2And the like.
The 2 nd magnetic layer 4b is a magnetic layer on the outermost layer side, and is a magnetic layer having a granular structure in which the grain boundary part 42 contains nitride. As described above, magnetic layers having a granular structure are often used in magnetic recording media, but since it is necessary to improve corrosion resistance, a magnetic layer having a non-granular structure is used as the magnetic layer on the outermost layer side. Therefore, not only improvement of the noise characteristics of the magnetic recording medium is hindered, but also high recording density of the magnetic recording medium is hindered because the magnetic grains on the outermost layer side of the magnetic layer are larger than those on the lower layer side.
In the present embodiment, the 2 nd magnetic layer 4b having a granular structure in which the grain boundary part 42 includes nitride is used as the magnetic layer on the outermost layer side, but since nitride is stable as compared with oxide, the corrosion resistance of the magnetic recording medium 10 can be improved. Further, since the 2 nd magnetic layer 4b has a granular structure, the magnetic grains can be isolated and made finer, and the noise characteristics of the magnetic recording medium can be improved, as in the 1 st magnetic layer 4 a.
On the other hand, as described above, since nitrides are stable and have low reactivity, it is difficult to form a magnetic layer having a granular structure in which a nitride is included in a grain boundary portion by a sputtering method.
Therefore, in the present embodiment, the following method is adopted as a method for forming the 2 nd magnetic layer 4 b. That is, after the magnetic layer having a non-granular structure is formed by the sputtering method, the magnetic layer having a non-granular structure is subjected to nitriding treatment to nitride a part of the element contained in the magnetic particles to form a grain boundary portion as a magnetic layer having a granular structure.
The nitride of the element contained in the magnetic particle of the present embodiment is preferably a nitride of boron, titanium, chromium, aluminum, tantalum, zirconium, or silicon.
Examples of the material constituting the magnetic layer having a non-granular structure according to the present embodiment include materials of a CoCrPt system, a CoCrPtB system, a CoCrPtTa system, a CoCrPtTi system, a cocrpttr system, a cocrptadal system, and a CoCrPtSi system.
The material constituting the non-granular magnetic layer of the present embodiment is suitable for deposition by sputtering.
As a method for nitriding the magnetic layer having a non-granular structure, a known method can be used, but in order to reduce damage to the magnetic layer, a method of exposing (exposing) the magnetic layer to reactive nitrogen plasma is preferably used.
By the nitriding treatment of the non-granular magnetic layer of the present embodiment, a part of the elements contained in the magnetic particles is nitrided to form a grain boundary portion, and the non-granular magnetic layer can be changed to a granular magnetic layer. The nitride of the element contained in the magnetic grains formed in this way is stronger and more stable than the nitride formed by the sputtering method, and therefore the corrosion resistance of the magnetic recording medium 10 can be improved.
Examples of the material constituting the 2 nd magnetic layer 4b include CoCrPt-CrN, CoCrPtB-BN, CoCrPtTa-TaN, CoCrPtTi-TiN, CoCrPtZr-ZrN, CoCrPtAl-AlN, CoCrPtSi-Si3N4And the like.
Examples of the material constituting the 2 nd magnetic layer 4b in the case where all the specified elements contained in the magnetic grains are nitrided include CoPt-CrN, CoCrPt-BN, CoCrPt-TaN, CoCrPt-TiN, CoCrPt-ZrN, CoCrPt-AlN, and CoCrPt-Si3N4And the like.
In this embodiment, by employing a method of nitriding a magnetic layer having a non-granular structure to form a magnetic layer having a granular structure, the 2 nd magnetic layer 4b which is chemically stable and has high corrosion resistance can be easily formed, as compared with a case of forming a nitride magnetic layer having a granular structure by a sputtering method.
In the present embodiment, the perpendicular magnetic layer 4 is provided with arbitrary magnetic layers or nonmagnetic layers 7a, 7b, 7c, 7d, 7e, and among them, 7a and 7c are preferably magnetic layers, and 7b, 7d, 7e are preferably nonmagnetic layers. Through these layers, the magnetic particles or non-magnetic particles 41 can form columnar crystals that are continuous from the lower layer to the upper layer of the perpendicular magnetic layer 4.
The number of optional magnetic layers or nonmagnetic layers may be increased or decreased as necessary.
As in the case of the 1 st magnetic layer 4a, any of the magnetic layers is preferably a magnetic layer having a granular structure in which a grain boundary portion includes an oxide.
The material constituting any of the magnetic layers is the same as that of the 1 st magnetic layer 4 a.
An optional nonmagnetic layer is disposed between the magnetic layers to control the exchange bonding (coupling) between the magnetic layers.
The material constituting any of the nonmagnetic layers is preferably a material having an hcp structure.
Examples of the material constituting the optional nonmagnetic layer include Ru, Ru alloys, RuCo alloys, CoCr alloys, and CoCrX1 alloys (here, X1 is 1 or 2 or more selected from Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Ti, V, Zr, and B).
As an arbitrary nonmagnetic layer, a nonmagnetic layer having a granular structure may be used.
The thickness of any nonmagnetic layer needs to be within a range in which ferromagnetic bonding between the 1 st magnetic layer 4a, the 2 nd magnetic layer 4b and any magnetic layer is not completely broken.
The protective layer 5 serves to prevent corrosion of the perpendicular magnetic layer 4 and also to prevent damage to the surface of the magnetic recording medium when the magnetic head is in contact with the magnetic recording medium.
As the material constituting the protective layer 5, a material used in the related art can be used.
As the protective layer 5, for example, a layer containing a hard carbon film can be used.
The thickness of the protective layer 5 is preferably 1 to 10 nm. This makes it possible to reduce the distance between the magnetic head and the magnetic recording medium, and to provide a magnetic recording medium suitable for increasing the recording density.
As a material constituting the lubricating layer 6, for example, a lubricant such as perfluoropolyether (perfluoropolyether), fluoroalcohol (fluorinated alcohol), fluorinated carboxylic acid (fluorinated carboxylic acid), or the like can be used.
Fig. 3 shows an example of the magnetic recording and reproducing device of the present embodiment.
The magnetic recording and reproducing apparatus shown in fig. 3 includes: a magnetic recording medium 10 (see fig. 1); a medium drive unit 11 for rotationally driving the magnetic recording medium 10; a magnetic head 12 for recording and reproducing information to and from the magnetic recording medium 10; a magnetic head driving unit 13 for moving the magnetic head 12 relative to the magnetic recording medium 10; and a recording/reproducing signal processing system 14.
The recording/reproducing signal processing system 14 may process data input from the outside and transmit the recording signal to the magnetic head 12, and may also process a reproducing signal from the magnetic head 12 and transmit the data to the outside.
As the magnetic head 12, a magnetic head suitable for high recording density, such as a Giant Magnetoresistive (GMR) element using GMR as a reproducing element, can be used.
[ examples ]
(example 1)
A magnetic recording medium was produced as follows.
A cleaned nonmagnetic substrate 1 (made by HOYA Co.) made of glass having an outer diameter of 2.5 inches was placed in a film forming chamber of a DC magnetron (magnon) sputtering apparatus C-3040 (made by ANELVA Co.), and the film forming chamber was evacuated to an ultimate vacuum degree (ultimate vacuum) of 1X 10-5After Pa, an adhesion layer having a thickness of 10nm was formed on the nonmagnetic substrate 1 using a target material of Cr-50 Ti { Ti content of 50 at%, balance Cr }.
Then, a soft magnetic layer having a thickness of 25nm was formed on the adhesion layer by using a Co-20 Fe-5 Zr-5 Ta { the content of Fe is 20 at%, the content of Zr is 5 at%, the content of Ta is 5 at%, and the balance is Co } target, while keeping the temperature of the nonmagnetic substrate 1at 100 ℃ or lower. Then, a Ru layer with a thickness of 0.7nm was formed on the soft magnetic layer using a Ru target. Next, a soft magnetic layer having a thickness of 25nm was formed as the soft magnetic underlayer 2 on the Ru layer using a Co-20 Fe-5 Zr-5 Ta target material with the temperature of the nonmagnetic substrate 1 set to 100 ℃ or lower.
Next, an Ni-6W layer having a thickness of 5nm and an Ru layer having a thickness of 20nm were formed in this order as orientation controlling layer 3 on soft magnetic underlayer 2 using an Ni-6W { W content of 6 at%, with the remainder being Ni } target and an Ru target, respectively.
Next, 91(Co15Cr18Pt) -6 (SiO) was used2)-3(TiO2) { Cr content of 15 at%, Pt content of 18 at%, and the remainder of the Co alloy content of 91 mol%, { SiO%2Content of (2) is 6 mol%, TiO2Is 3 mol% } target material, is arranged on the alignment control layer 3The magnetic layer 7a had a granular structure with a thickness of 9 nm. At this time, the sputtering pressure was 2 Pa.
Next, 88(Co30Cr) -12 (TiO) was used2) { Cr content 30 at%, Co content in the remainder 8 mol%, TiO2Is 12 mol% } target material, and a nonmagnetic layer 7b of a granular structure having a thickness of 0.3nm is formed on the magnetic layer 7 a.
Next, 92(Co11Cr18Pt) -5 (SiO) was used2)-3(TiO2) { Cr content of 11 at%, Pt content of 18 at%, and the remainder of the Co alloy content of 92 mol%, { SiO%2Content of (2) is 5 mol%, TiO2Is 3 mol% } target material, and the 1 st magnetic layer 4a having a thickness of 6nm is formed on the nonmagnetic layer 7 b. At this time, the sputtering pressure was 2 Pa.
Next, a nonmagnetic layer 7e having a non-granular structure with a thickness of 0.3nm was formed on the 1 st magnetic layer 4a using a Ru target.
Next, a magnetic layer having a non-granular structure and a thickness of 10nm was formed on the nonmagnetic layer 7e using a target of Co10Cr20Pt14B { the Cr content is 10 at%, the Pt content is 20 at%, the B content is 14 at%, and the balance is Co }. At this time, the sputtering pressure was 0.6 Pa.
Subsequently, the non-granular magnetic layer was exposed to reactive nitrogen plasma for 20 seconds to be nitrided, and the second magnetic layer 4B was formed as a granular-structure magnetic layer composed of 93(Co12Cr22Pt7B) -7 (BN) { Cr content of 12 at%, Pt content of 22 at%, B content of 7 at%, the remainder of the Co alloy content of 93 mol%, and BN content of 7 mol% }. At this time, the reactive nitrogen plasma was generated by applying RF power (500W) to a mixed gas having a nitrogen content of 5 vol% and an argon content of 95 vol%.
Next, a protective layer 5 having a thickness of 3nm was formed on the second magnetic layer 4b by an ion beam method.
Next, a lubricating layer 6 composed of perfluoropolyether was formed on the protective layer 5 by a dipping method (nipping), thereby obtaining a magnetic recording medium 10.
(example 2)
A magnetic recording medium 10 was obtained in the same manner as in example 1, except that a magnetic layer having a granular structure of 93(Co12Cr22Pt7Ti) -7 (TiN) was formed using a Co10Cr20Pt14Ti target in forming the second magnetic layer 4 b.
(example 3)
A magnetic recording medium 10 was obtained in the same manner as in example 1, except that a magnetic layer having a granular structure of 93(Co12Cr22Pt7Al) -7 (AlN) was formed using a target of Co10Cr20Pt14Al when forming the second magnetic layer 4 b.
(example 4)
A magnetic recording medium 10 was obtained in the same manner as in example 1, except that a magnetic layer having a granular structure of 93(Co12Cr22Pt7Ta) -7 (TaN) was formed using a target of Co10Cr20Pt14Ta when forming the second magnetic layer 4 b.
(example 5)
A magnetic recording medium 10 was obtained in the same manner as in example 1, except that a magnetic layer having a granular structure of 93(Co12Cr22Pt7Zr) -7 (ZrN) was formed using a Co10Cr20Pt14Zr target in forming the second magnetic layer 4 b.
(example 6)
Except that a material consisting of 96(Co12Cr22Pt2Si) -4 (Si) was formed using a Co10Cr20Pt14Si target in forming the second magnetic layer 4b3N4) A magnetic recording medium 10 was obtained in the same manner as in example 1 except for the magnetic layer having the granular structure.
Comparative example 1
A magnetic recording medium was obtained in the same manner as in example 1, except that a magnetic layer having a non-granular structure of Co10Cr20Pt14B was formed without performing nitriding treatment when forming the second magnetic layer 4 b.
Comparative example 2
Except that 92(Co11Cr18Pt) -5 (SiO) was used in forming the second magnetic layer 4b2)-3(TiO2) The target material is formed by 92(Co11Cr18Pt) -5 (SiO)2)-3(TiO2) A magnetic recording medium was obtained in the same manner as in example 1 except for the magnetic layer having the granular structure.
(composition of the 1 st magnetic layer 4a and the 2 nd magnetic layer 4 b)
The composition of the 1 st magnetic layer 4a and the 2 nd magnetic layer 4b was measured by XPS.
Next, the magnetic recording medium was evaluated for noise characteristics and corrosion resistance.
(noise characteristics)
The SNR (signal-to-noise ratio (S/N ratio)) which is a recording/reproducing characteristic of a magnetic recording medium was evaluated using a read-write analyzer (RWA 1632) and a spin stand (spin stand) S1701MP (GUZIK).
(Corrosion resistance)
The corrosion resistance of the magnetic recording medium was evaluated by counting the number (number/surface) of pits (corrosion spots) generated on the surface of the magnetic recording medium using an optical surface inspection machine after the magnetic recording medium was left to stand for 96 hours in an environment with a temperature of 90 ℃ and a humidity of 90% RH. In this case, the detection accuracy is set to be 5 μm or more in diameter.
Table 1 shows the evaluation results of the noise characteristics and corrosion resistance of the magnetic recording medium.
[ Table 1]
Figure BDA0001498140930000161
As is clear from table 1, the magnetic recording media of examples 1 to 6 are excellent in noise characteristics and corrosion resistance, and suitable for increasing the recording density.
However, in the magnetic recording medium of comparative example 1, since the magnetic layer on the outermost layer side is a magnetic layer having a non-granular structure, the noise characteristics are degraded, and it is not suitable for increasing the recording density.
In the magnetic recording medium of comparative example 2, although the magnetic layer on the outermost layer side was a granular magnetic layer, the grain boundary portion included silicon oxide and titanium oxide, and therefore corrosion resistance was significantly reduced, and noise characteristics were also reduced due to the influence of the silicon oxide and titanium oxide, and it was not suitable for increasing the recording density.
In view of the above, a magnetic recording medium is provided that has a soft magnetic underlayer, an alignment control layer, a perpendicular magnetic layer, and a protective layer in this order on a non-magnetic substrate. The perpendicular magnetic layer has a1 st magnetic layer and a 2 nd magnetic layer in this order from the non-magnetic substrate side. The 2 nd magnetic layer is a magnetic layer on the outermost layer side containing magnetic particles. The 1 st magnetic layer is a magnetic layer having a granular structure in which a grain boundary portion contains an oxide. The 2 nd magnetic layer is a magnetic layer having a granular structure in which a grain boundary portion contains a nitride. The nitride is a nitride of an element contained in the magnetic particle.
In the magnetic recording medium, the element contained in the magnetic particles is boron, titanium, chromium, aluminum, tantalum, zirconium, or silicon.
In the magnetic recording medium, the oxide is an oxide of silicon, chromium, titanium, tantalum, aluminum, yttrium, boron, magnesium, tungsten, or cobalt.
In addition, a method for manufacturing a magnetic recording medium having a soft magnetic underlayer, an alignment control layer, a perpendicular magnetic layer, and a protective layer in this order on a non-magnetic substrate is also provided. The step of forming the perpendicular magnetic layer includes the step of forming the 1 st magnetic layer and the step of forming the 2 nd magnetic layer in this order. The 2 nd magnetic layer is formed as a magnetic layer on the outermost layer side containing magnetic particles. The step of forming the 1 st magnetic layer is a step of forming a magnetic layer having a granular structure in which an oxide is included in a grain boundary portion by a sputtering method. The step of forming the 2 nd magnetic layer is a step of forming a magnetic layer having a granular structure by forming a magnetic layer having a non-granular structure by a sputtering method and then nitriding the magnetic layer to form a grain boundary portion by nitriding a part of elements contained in the magnetic particles.
In the method for manufacturing a magnetic recording medium, the nitrided element is boron, titanium, chromium, aluminum, tantalum, zirconium, or silicon.
In the method for manufacturing a magnetic recording medium, the oxide is an oxide of silicon, chromium, titanium, tantalum, aluminum, yttrium, boron, magnesium, tungsten, or cobalt.
Further, a magnetic recording/reproducing apparatus is provided with the magnetic recording medium and a magnetic head for recording and reproducing information to and from the magnetic recording medium.
Although the embodiments of the present invention have been described above, the above description is not intended to limit the contents of the present invention.

Claims (5)

1. A magnetic recording medium having a soft magnetic underlayer, an alignment control layer, a perpendicular magnetic layer, and a protective layer in this order on a non-magnetic substrate, wherein:
the perpendicular magnetic layer has a1 st magnetic layer and a 2 nd magnetic layer in this order from the non-magnetic substrate side,
the 2 nd magnetic layer is a magnetic layer on the outermost layer side containing magnetic particles,
the 1 st magnetic layer is a magnetic layer having a granular structure in which a grain boundary portion contains an oxide,
the 2 nd magnetic layer is a magnetic layer having a granular structure in which a grain boundary portion contains a nitride,
the nitride is a nitride obtained by nitriding an element contained in the magnetic particle,
the element contained in the magnetic particles is boron, titanium, chromium, aluminum, zirconium, or silicon.
2. A magnetic recording medium according to claim 1, wherein:
the oxide is an oxide of silicon, chromium, titanium, tantalum, aluminum, yttrium, boron, magnesium, tungsten, or cobalt.
3. A method for manufacturing a magnetic recording medium having a soft magnetic underlayer, an alignment control layer, a perpendicular magnetic layer, and a protective layer in this order on a nonmagnetic substrate, wherein:
the step of forming the perpendicular magnetic layer includes a step of forming a1 st magnetic layer and a step of forming a 2 nd magnetic layer in this order,
forming the 2 nd magnetic layer as a magnetic layer on the outermost layer side containing magnetic particles,
the 1 st magnetic layer forming step is a step of forming a magnetic layer having a granular structure in which an oxide is contained in a grain boundary portion by a sputtering method,
the step of forming the 2 nd magnetic layer is a step of forming a magnetic layer having a granular structure by forming a magnetic layer having a non-granular structure by a sputtering method, and then nitriding the magnetic layer to form a grain boundary portion by nitriding a part of an element contained in the magnetic particles,
the nitriding element is boron, titanium, chromium, aluminum, zirconium or silicon.
4. A manufacturing method of a magnetic recording medium according to claim 3, wherein:
the oxide is an oxide of silicon, chromium, titanium, tantalum, aluminum, yttrium, boron, magnesium, tungsten, or cobalt.
5. A magnetic recording/reproducing apparatus includes:
a magnetic recording medium according to claim 1 or 2; and
and a magnetic head for recording and reproducing information to and from the magnetic recording medium.
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